This research will examine the role of the forelimb, trunk muscles, and iliosacral joint in frog jumping. The primary goal is to incorporate data from these elements into an existing realistic musculoskeletal model of the frog (Rana pipiens). To achieve this objective, I will utilize muscle mechanics experiments, whole animal jumping, and forward dynamic simulation to provide a detailed characterization of frog locomotion. The primary focus is understanding the design and function of the trunk muscles, iliosacral joint, and forelimbs in frog jumping. The reason for this focus is that these components are thought to play a key role in positioning the anterior part of the body with the hindlimb generated propulsive force. Preliminary results indicate the role of the forelimbs is more complex than is generally appreciated. The proposed study will test these ideas, with the end result being a more complete understanding of the frog musculoskeletal system from the molecular to the whole animal level. Once completed, the current model will be modified to reflect ancestral musculoskeletal designs. Comparing jumping performance among those designs will provide unique insight into the evolutionary history that produced the modem form-function complex in frogs.